As the conventional fixing apparatus of this type, there has hitherto been known an apparatus in which a plurality of (first and second) rolls around a heating roll are respectively brought into rotational contact with the heating roll to form nips, respectively, the rolls being positioned upper in the direction of gravity than the rotational shaft of the heating roll (see, e. g., JP 2006-330340 A).
In the makeup of such a prior-art fixing apparatus as cited above, two rollers around a heating roller are arranged spaced apart from each other by a distance in the direction of rotation of the heating roller and are brought into rotational contact with the heating roller. Then, a sheet of paper traveling as the heating roller rotates may float, leaving the heating roller in between the two rollers.
When a sheet of paper floats upon passing the first roller, problems arise. Thus, the nip by the second and heating rollers tends to cause such a sheet of paper to become crinkled. The higher the speed of transport of a sheet of paper becomes, the less sufficient the feed of fixing heat to the sheet of paper will be. In addition, the leading end of the sheet of paper on the way of its transport from the first nip to the second nip is freed, thereby making the transport per se unstable.
With the preceding problems taken into account, it is an object of the present invention to provide a fixing apparatus for a sheet-fed electrophotographic printer whereby a sheet of paper even in transport at higher speed can be transported stably without causing sheet crinkling and can be supplied enough with fixing heat, thereby achieving thermal fixing of an image with stabilized printing quality at higher speed.